Serum interleukin-18 levels can improve the diagnostic performance of the PRINTO and ILAR criteria for systemic juvenile idiopathic arthritis.

ABSTRACT

OBJECTIVE: Recently, the Pediatric Rheumatology International Trials Organization (PRINTO) has proposed revisions to the current International League of Associations for Rheumatology (ILAR) criteria for systemic juvenile idiopathic arthritis (s-JIA). Interleukin (IL)-18 overproduction plays a significant role in the pathogenesis of s-JIA. This study aimed to evaluate the performance of the PRINTO criteria compared with the ILAR criteria and determine whether serum IL-18 levels improve their diagnostic performances. METHODS: Overall, 90 patients with s-JIA and 27 patients with other febrile disease controls presenting with a prolonged fever of > 14 days and arthritis and/or erythematous rash were enrolled. The ILAR and PRINTO classification criteria were applied to all patients and examined with expert diagnoses. Enzyme-linked immunosorbent assay was used for measuring serum IL-18 levels. RESULTS: The PRINTO criteria had higher sensitivity but lower specificity than the ILAR criteria (sensitivity PRINTO 0.856, ILAR 0.533; specificity PRINTO 0.259, ILAR 0.851). With the addition of serum IL-18 levels ≥ 4,800 pg/mL, the sensitivity of the ILAR criteria and specificity of the PRINTO criteria were improved to 1.000 and 1.000, respectively. PRINTO plus serum IL-18 levels ≥ 4,800 pg/mL showed the highest value in Youden's index (sensitivity - [1 - specificity]). CONCLUSION: Serum IL-18 levels could improve the diagnostic performance of the PRINTO and ILAR criteria for s-JIA. The PRINTO criteria plus serum IL-18 levels ≥ 4,800 pg/mL could be the best diagnostic performance for s-JIA.